When a surface is at a temperature on or below the dew point of the prevailing atmosphere, water condenses on the surface in the form of small droplets. When the condensation is on transparent or reflecting surfaces it is referred to as "fogging." This problem of fogging is critical for some applications and at least troublesome for many others. Substrates of plastic, glass, and metal surfaces all fog without some modification. Many attempts have been made to reduce or eliminate the fogging problem particularly for automobile windshields and safety goggles. Early attempts included the application of films containing glycerol and more recently coatings based on hydroxy substituted acrylic polymers have been offered (see U.S. Pat. No. 3,488,215 issued to Shepherd et al.) Other coatings offered to reduce the fogging of surfaces include films containing surfactants and more recently U.S. Pat. No. 3,411,945 issued to Chao describes the incorporation of surfactants in the thermoplastic polymer substrate to reduce the tendency towards fogging of the surface.
Accordingly, it is an object of the present invention to provide a non-fogging surface that does not interfere with the transparency or reflectance of the substrate material. An additional object is to provide a transparent, non-fogging coating with improved permanence of the anti-fogging protection, increased adhesion to the substrate, improved scratch and abrasion resistance, improved durability of the adhesion to the substrate and improved durability of the surface of the coating.
An additional object is to provide a transparent coating that will reduce the fogging characteristics for transparent or reflecting surfaces that may be easily applied to the surfaces to provide consistent results. A more specific object is to prepare a transparent, non-fogging coating for transparent or reflecting surfaces of glass, plastic or metal. An object is to provide anti-fogging eye lenses and protective shields, windows and mirrors.
An additional object is to provide a transparent anti-fogging coating for transparent substrates, particularly polycarbonate, with improved permanence and abrasion resistance. A more specific object is providing a novel composition of matter that is hard, resistant to detergent solutions and adheres to substrates while imparting anti-fogging characteristics.